Control circuit unit for a variable capacity compressor incorporating a solenoid-operated capacity control valve

Abstract

A control circuit unit for controlling the energization of a solenoid of a solenoid-operated capacity control unit incorporated in a a variable capacity compressor, typically, a variable capacity wobble plate type refrigerant compressor for a car air-conditioner, having a switching unit for establishing an electric conduction of the energizing circuit of the solenoid when the solenoid-operated valve is actuated for changing the compressor capacity, and an electric energizing voltage control circuit used to apply a high electric starting voltage to the solenoid emergizing circuit at a predetermined initial starting time of the solenoid, and a low electric retaining voltage required for retention of the energization of the solenoid valve after the predetermined starting time has elapsed.

We claim: 
     
       1. A control circuit for controlling an operation of a solenoid-operated capacity control unit of a variable capacity refrigerant compressor accommodated in an air-conditioning system of an automobile and provided with a compressor framework having therein a suction chamber for a refrigerant to be compressed and a discharge chamber for a compressed refrigerant to be discharged to the air-conditioning system, a rotatable drive shaft connectable to a rotation drive source, a variable capacity compressing unit for sucking, compressing and discharging the refrigerant in response to the rotation of the drive shaft, and a capacity control refrigerant passageway means for controlling a pressure acting on the variable capacity compressing unit, said capacity control refrigerant passageway means being opened and closed by an operation of a valve element of the solenoid-operated capacity control unit, said control circuit comprising: a single DC electric power source for supplying electric voltage to a solenoid of said solenoid-operated capacity control unit, said electric switching circuit means comprising two parallel transistor switching circuits arranged in an electric energizing circuit of said solenoid of said solenoid-operated capacity control unit for permitting an application of a high DC voltage to the electric circuit of the solenoid when both of the parallel transistor switching circuits are turned ON, and permitting an application of a low DC voltage to the electric energizing circuit of the solenoid when only one of the parallel transistor switching circuits is turned ON; and   electric energizing voltage control circuit means for controlling the level of said electric voltage applied to said electric energizing circuit of said solenoid from said single electric power source in such a manner that a high level electric starting voltage needed to initiate a movement of the valve element of said solenoid-operated capacity control unit is applied to said electric energizing circuit of said solenoid for a predetermined time, through said two parallel transistor switching circuits, and that after said predetermined time has elapsed, a low level electric retaining voltage needed to retain said solenoid of said solenoid-operated capacity control unit at an energized position is applied through said only one of said two parallel transistor switching circuits.   
     
     
       2. A control circuit means according to claim 1, wherein said electric energizing voltage control circuit means comprises time delay circuit means for changing said electric voltage applied to said solenoid from said high level electric starting voltage to said low level electric retaining voltage after said predetermined time has elapsed. 
     
     
       3. A control circuit means according to claim 2, wherein said time delay circuit means comprises a time constant circuit including electric capacity element means for electrically determining said predetermined time and electric resistance element means for determining said low level electric retaining voltage applied to said solenoid. 
     
     
       4. A control circuit means as claimed in claim 1, wherein said two parallel transistor switching circuits of said electric switching circuit means comprises first and second transistor means for establishing an electric conduction of said electric energizing circuit of said solenoid of said solenoid-operated capacity control unit when said transistor means are turned ON, said first transistor means having a base thereof to which a gradually decreased electric switching voltage is supplied for said predetermined time to establish said high level starting voltage for said predetermined time, and said second transistor means having a base thereof to which a constant switching voltage is applied to establish said low level electric retaining voltage after said predetermined time has elapsed. 
     
     
       5. A control circuit means as claimed in claim 1, wherein said variable capacity refrigerant compressor comprises a variable capacity wobble plate type compressor incorporating said solenoid-operated capacity control unit in said framework including a crankcase and a cylinder block.